[tex] 1^{3} + 2^{3}+.......+ n^{3} = (\frac{n(n+1)}{2} )^{2} [/tex]
La a) dai factor 2*3*4 iar la b) factor 1*2*3, in paranteze ramae ([tex] 1^{3} + 2^{3} + . . . + 12^{3} = (\frac{12(12+1)}{2})^{2} [/tex]. Apoi inlocuest, nu are rost sa faci ridicarile la putere si inmultirile.
